Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$223.39	6.490%	$237.888	$237.89	$237.90	$237.90
Purchase #2	$132.85	9.363%	$145.2887	$145.29	$145.30	$145.30
Purchase #3	$94.87	11.243%	$105.5362	$105.54	$105.55	$105.50
Purchase #4	$231.48	4.599%	$242.1258	$242.13	$242.15	$242.10
Purchase #5	$46.60	7.302%	$50.0027	$50.00	$50.00	$50.00
Purchase #6	$78.77	12.546%	$88.6525	$88.65	$88.65	$88.70
Purchase #7	$144.91	3.729%	$150.3137	$150.31	$150.30	$150.30
7 purchase totals =	$952.87		$1,019.8076	$1,019.81	$1,019.85	$1,019.80